The present invention relates to a mechanical microscope stage having provision for fine adjustment for precise positioning of the stage and having a handle for rapid displacement of the stage when the fine adjustment is disconnected.
Such mechanical stages, having X-Y slides for two-axis displacement of a specimen, are needed in optical inspection of so-called wafers, i.e., semiconductor substrates, where rapid scanning of the specimen and precise adjustment of individual partial regions are both required.
The mechanical stages which have thus far been used for this purpose have, in addition to providing fine-adjustment for the precise displacement of the stage (wherein the fine-adjustment means is at one lateral side of the stage and employs coaxial elements with a strong step-down ratio), also provides a handle for rapid displacement of the stage, the handle being arranged directly on the movable stage plate, and also on one lateral side thereof. In such a stage, as for example the stage described in GB-A-2,079,969, the handle is approximately at the same height as the surface of the stage. However, this arrangement results in increased danger of contaminating the specimen, which must be examined under clean-room conditions. It is therefore customary to form the rapid-displacement handle as a downwardly bent yoke which is arranged at one side of the stage and can be gripped below the plane of the stage. This solution, however, is also unsatisfactory since with such a laterally disposed yoke, the point of actuating-force application is at some distance from the stage guides, and a long yoke is unstable.
Furthermore, a lateral positioning of the handle is ergonomically unfavorable since it must necessarily favor a given hand of the operator and does not permit optional gripping by the other hand, which may happen to be free at the time; such handle positioning thus requires frequent groping for the handle.
Austrian Patent No. 314,861 discloses a mechanical stage suitable for examining semiconductor substrates wherein a common handle serves for fine positioning and rapid displacement. The handle is in the form of a lever which is mounted in a ball socket. The lever can be guided along a template which is secured alongside the stage. But this lever is also disposed on one side of the stage, far from its guides, so that the stage is thereby given a projecting and not very compact shape which interferes with attachment of such additional instrumentalities as an automatic conveyor unit for feeding or removal of the specimens.
Federal Republic of Germany Utility Model No. 1,311,435 and German Democratic Republic Pat. No. 95,121 also disclose mechanical stages in which the fine adjustment is located centrally below the stage. These mechanical stages, however, do not have a handle for rapid displacement when the fine adjustment is disconnected.